1. Field of the Invention
This invention pertains to a hydraulically regulated pad for use within the interior of footwear to adjust to the specific space requirements of a foot as they vary during regular usage. More specifically, the present invention relates to a pad comprised of multiple compartments which permit the shifting of hydraulic fluid in response to forces applied to the footwear, such as through a buckle-closure system in a ski boot.
2. Prior Art
The difficulty of maintaining a comfortable fit of rigid footwear around the human foot represents a significant challenge. Each person has a foot shape which tends to be quite unique. This uniqueness not only extends to the dimensions in length and widths along the contours of the foot, but also to the arches and cavities. Achieving adequate support over the total foot surface is much more complicated, therefore, than taking linear measurements for the total confinement area. The various sizes of arches below and above the foot, as well as around the heel must also be considered.
Undoubtedly, the most demanding requirements for true fit footwear occur within sports activities. In this environment, froces applied to the foot test the adequacy of support and comfort. Furthermore, this support must respond to the dynamics of the sport. Abrupt movements and impacts are translated through the footwear and into the foot. Such influences result in significant modifications to the shape of the foot, which must be supported and protected for safety, as well as comfort.
Perhaps the most demanding footwear requirements arise in ski boots. Here, the foot is subject to changing forces with each change in terrain and movement. These forces are applied over the total surface of the foot, and not merely on the sole. For example, it is the foot and ski boot that control the turn, direction, glide and general action of the ski. Therefore, a snug, form-fit must be maintained in order to preserve response of the ski to each movement of the foot. Lack of proper fit leads to vertical and/or lateral sliding of the foot within the boot and resultant loss of control.
A particularly troublesome problem is the difficulty of keeping the heel in its seated position at the heel of the boot. Conventional skiing techniques require the skier to lean forward to maintain control of the skis. Although this operates to place the desired force at the tips of the skis, it also tends to lift the heels from their seated position. As the heels leave the heel socket, the ability of the skier to control lateral turns is significantly impaired.
It is therefore well known that proper fit of a ski boot in a static or standing condition does not ensure that adequate comfort and support will exist while traversing downhill terrain. Indeed, the more significant fit is the "dynamic" fit required during actual skiing activity. Unfortunately, this fit is very difficult to capture in a single mold because the shape and position of the foot is changing with each impact and new direction of movement. Hence, the dilemma exists of how to develop a fit which feel comfortable during both static and dynamic conditions, while maintaining the foot is a fully seated position within the ski boot.
Numerous attempts have been made to develop a more fluid type of containment for the foot. Inner linings of silicone powder have been made which are designed to improve form-fit of the boot. These have been unsuccessful in producing the type of dynamic adjustability needed. Single fluid pockets have been applied within a ski boot; however, these have not provided the required dynamic response necessary to keep the heel in position or provide a changing interior during actual skiing activity.